Category: SQL Lessons

As a developer my favorite new feature of SQL Server 2016 is JSON support.

I love JSON in SQL because I already love JSON everywhere outside of SQL: it uses much less space than XML for serializing data, it’s what most apps are now using for API communication, and when web developing I love that it is already valid JavaScript (no need to deserialize!).

I had this same type of excitement for XML in SQL Server, but after using it the excitement quickly turned into disappointment: having to constantly use the XML datatype was inconvenient (when most XML data I used was already stored in nvarchar(max) columns) and I never found the syntax of OPENXML() to be that intuitive.

Everything I’ve done with JSON in SQL Server 2016 so far has been great. I’ve already been storing persistent JSON in SQL, so being able to manipulate JSON within SQL is even better. In this series of posts I will go over the various functionalities of using JSON in SQL Server 2016:

Part 1 — Parsing JSON

What is JSON?

My simple, mostly caveat-free* explanation is that it is a format for storing object data in JavaScript. It’s lightweight and easy to read, so it’s used in lots of applications that aren’t just JavaScript (although it’s especially easy to consume in JavaScript because it is JavaScript*).

Strict versus Lax mode

For any of the SQL JSON functions (OPENJSON(), JSON_VALUE(), JSON_QUERY(), andJSON_MODIFY()) you can specify whether invalid JSON paths will return NULL or an error. The default value is lax, which will return a NULL for non-existing JSON paths, whereas strict will return an error message.

OPENJSON()

While JSON_VALUE() extracts singular scalar values and JSON_QUERY() extracts singular JSON strings, the OPENJSON() function extracts result sets from a JSON string. In addition to the extracted value, OPENJSON() outputs the order of JSON objects as well as their datatypes. OPENJSON() will also output string representations of JSON arrays instead of just displaying NULL, similar to JSON_QUERY().

The flexibility of OPENJSON() makes it possible to extract any values from JSON data, especially when combining OPENJSON() with JSON_VALUE(). The examples below show how to parse out a scalar value from complex JSON objects (like arrays). Note that using the WITH option gives us a lot more flexibility with how we can format our output result.

These JSON functions should help you parse any JSON data you encounter in SQL server (as long as it’s valid and stored as nvarchar). Stay tuned over the next few weeks as we look at other SQL JSON functions that will help us create data, modify data, and compare SQL’s JSON performance to other languages.